1. Field of the Invention
This invention relates to electrical connectors for printed circuit boards (i.e., printed wiring boards). More particularly, it relates to card edge connectors and the corresponding female sockets for such connectors, such as sockets used within a personal computer used to electrically connect adapter, peripheral and expansion cards to the personal computer expansion slots.
2. Description of the Prior Art
Printed circuit boards ("PCB's") are often provided with card edge connectors for the purpose of making electrical connection to the PCB. The card edge connector consists of a projection along an edge of the PCB which is provided with an array of generally planar, exposed metal pads on either side of the projection. Although other spacings are possible and have been used, these contact pads are typically spaced apart 0.100 inch on center to make the alignment between PCB edge and mating connector less critical and are often gold-plated to make them corrosion resistant and to provide an electrical connection with negligible contact resistance. A card edge connector is, therefor a male electrical connector.
The female socket for a card edge connector typically comprises a slotted, molded plastic box with an elongated opening along its upper surface for receiving the projection on the PCB. The interior of the slot is lined with an array of inwardly-biased, spring-loaded contacts which are spaced to correspond to the exposed metal pads on the card edge connector. Typically, the spring-loaded contacts are the upper portion of solder pins which extend through the bottom of the socket in two parallel rows. These solder pins are designed for insertion into through-holes of a PCB "motherboard". The pins are subsequently pressed or soldered to the motherboard (most commonly in a wave soldering operation) to provide both electrical and mechanical connection to the PCB motherboard. The connector pins are also suitable for surface mounting techniques.
The first generation of personal computers such as the IBM PC and the Compaq Deskpro had 62-pin sockets on their motherboards for the card edge connectors of accessory circuit boards ("cards") such as disk controllers, modems, and the like. These devices typically operated with an 8-bit I/O bus.
The second generation of personal computer conforming to the industry standard architecture ("ISA") such as the Compaq Deskpro 286 computer, the IBM PC-AT computer, and the Hewlett Packard Vectra computer feature a 16-bit I/O bus and many accessory cards utilize the 16-bit bus. Accordingly, it was necessary to increase the number of contacts on card edge connectors and their corresponding sockets on the motherboard. This was accomplished by providing an additional 36-pin card edge connector in line with a conventional 62-pin card edge connector. Likewise, an additional 36-pin socket can be provided in line with the conventional 62-pin socket, or a single piece, 98-pin socket may be used for a 32-bit bus connection. Although straightforward, this solution is not practical because of the excessive use of board space. 16-bit accessory cards, compatible with the industry standard architecture, typically have a gap between the two portions of the card edge connector to bridge the abutting walls of the end-to-end sockets on the motherboard.
State-of-the-art personal computers now feature a 32-bit I/O bus. Accordingly, it is necessary to provide a means for increasing the number of contacts on card edge connectors. A straightforward solution to this problem would be to simply provide an additional card edge connector in line with the conventional connectors of ISA cards. However, the corresponding socket(s) take up valuable surface area on the motherboard. Another approach is to decrease the spacing between the pins thus providing a greater number of contacts in the same space. However, this approach fails to provide compatibility with existing 8- and 16-bit cards having conventional pin spacings.
The present invention solves this problem by providing both an increase in the number of available contacts in the same length card edge connector and compatibility with conventional 8- and 16-bit cards by providing contact spacing comparable with existing connectors.